Steering assist apparatus

ABSTRACT

A steering assist apparatus comprises a steering assist control means for performing a lane tracing assist control (LTA) and a lane changing assist control (LCA) and a non-holding determination means for determining whether or not a first non-holding condition that a non-holding duration time is more than or equal to a first time is satisfied and whether or not a second non-holding condition that the non-holding duration time is more than or equal to a second time shorter than the first time is satisfied. The steering assist control means raises a warning when the second non-holding condition becomes satisfied and stops the LTA when the first non-holding condition becomes satisfied while performing the LTA, and raises a warning when the second non-holding condition becomes satisfied whereas continues the LCA until a completion condition of the LCA becomes satisfied regardless of the non-holding while performing the LCA.

TECHNICAL FIELD

The present invention relates to a steering assist apparatus to assist adriver with a steering operation.

BACKGROUND ART

A steering assist apparatus applied to a vehicle and performing acontrol to assist a driver with a steering operation has beenconventionally known (refer to Japanese Patent Application Laid-Open(kokai) No. 2009-274594). This control to assist the driver with thesteering operation (hereinafter, this control is also referred to as a“steering assist control”) includes, for example, a lane tracing assistcontrol (hereinafter, also referred to as “LTA”), a lane changing assistcontrol (hereinafter, also referred to as “LCA”), and the like.

The LTA is a control to assist (support) the driver with the steeringoperation such that a traveling position of the vehicle is kept at apredetermined position in a lane in a lane width direction based on laneinformation including a relative positional relationship of the vehiclewith respect to the lane. The LCA is a control to assist the driver withthe steering operation such that the vehicle changes a lane from anoriginal lane on which the vehicle is currently traveling to a targetlane adjacent to the original lane based on the above lane information.Hereinafter, a vehicle in which the steering assist apparatus is mountedis also referred to as an “own vehicle”.

More specifically, in the steering assist control such as the LTA andthe LCA, a steered angle of each of steered wheels is controlled in sucha manner that a yaw angle (an angle formed by a direction along which alane is formed and a direction toward which the own vehicle is oriented)coincides with a target yaw angle. It should be noted that the targetyaw angle for the LTA is zero degree.

SUMMARY OF THE INVENTION

The steering assist control such as the LTA and the LCA is a controlmerely to assist (support) the driver of the own vehicle with thesteering operation, and therefore differs from an automatic drivecontrol. Hence, it is basically required for the driver to hold thesteering wheel during a performance of the steering assist control.However, there may be a case where the driver overestimates the steeringassist control and therefore does not hold the steering wheel in spiteof the steering assist control being performed.

Therefore, a following configuration is adopted, the configuration beinga configuration where the LTA is stopped when a time for which a statewhere the driver is not holding the steering wheel during a performanceof the LTA (hereinafter, this state is referred to as a “non-holdingstate”) is continuing (hereinafter, this time is referred to as a“non-holding duration time”) becomes more than or equal to apredetermined time. According to this configuration, the driver comes tohold the steering wheel when the driver has noticed that the LTA is notbeing properly performed (for example, a case where a state in which theyaw angle is not apparently zero degree is continuing) as a result ofthe non-holding duration time becoming more than or equal to thepredetermined time and the LTA being stopped. That is, by adopting thisconfiguration, it becomes possible to urge the driver to hold thesteering wheel during a performance of the LTA. Therefore, a situationwhere “the driver overestimates the steering assist control andtherefore does not hold the steering wheel in spite of the LTA beingperformed” can be suppressed from occurring.

However, a following problem occurs if the above configuration isapplied to the LCA. That is, for example, in a case where thenon-holding duration time has become more than or equal to thepredetermined time and the LCA is stopped when the own vehicle isstriding over “a white line positioned between the original lane and thetarget lane” (that is, when the yaw angle has a value of not being zero(a nonzero value)), the own vehicle continues to travel, maintaining theyaw angle with the nonzero value of a point in time when the LCA hasbeen stopped. However, to begin with, the LCA is a control to assist avehicle in changing a lane, and thus during a performance of thiscontrol, it is not particularly unnatural that the own vehicle travelswith a yaw angle of a nonzero value. Therefore, it becomes impossiblefor the driver to distinguish whether the LCA is being performed orstopped (that is, the driver misrecognizes that the LCA is beingperformed in spite of the LCA being stopped), and as a result, itbecomes highly likely that the own vehicle deviates from the target lanewithout the driver noticing and cannot change a lane properly.

The present invention is made to resolve the problem above. That is, oneof objects of the present invention is to provide a steering assistapparatus enabling a vehicle to properly change a lane by the LCA whilesuppressing a driver of the vehicle from overestimating a steeringassist control by urging the driver to hold a steering wheel during aperformance of the steering assist control.

A first steering assist apparatus of the present invention (hereinafter,may be referred to as a “first invention apparatus”) is applied to avehicle.

This first invention apparatus comprises;

lane recognition means (12) for recognizing a lane to acquire laneinformation including a relative positional relationship of the vehiclewith respect to the lane;

steering assist control means (10, 20) for performing a lane tracingassist control to assist a driver with a steering operation by changinga steered angle of a steered wheel of the vehicle such that a travelingposition of the vehicle is kept at a predetermined position in a lane ina lane width direction based on the lane information and a lane changingassist control to assist the driver with the steering operation bychanging the steered angle such that the vehicle changes a lane from anoriginal lane on which the vehicle is currently traveling to a targetlane adjacent to the original lane based on the lane information;

non-holding detection means (42) for detecting a non-holding state whichis a state where the driver of the vehicle is not holding a steeringwheel; and

non-holding determination means (S626, S610, S618) for measuring anon-holding duration time which is a time for which the non-holdingstate is continuing during a performance of either the lane tracingassist control or the lane changing assist control to determine whetheror not a first non-holding condition that the non-holding duration timeis more than or equal to a predetermined first time (tu) is satisfiedand whether or not a second non-holding condition that the non-holdingduration time is more than or equal to a predetermined second time (tw)shorter than the first time (tu) is satisfied,

wherein,

the steering assist control means (10, 20) is configured to;

-   -   during a performance of the lane tracing assist control,    -   warn the driver (S624) by means of at least one of sound, an        indication, and vibration when the second non-holding condition        is determined to be satisfied (S610: Yes); and    -   stop the lane tracing assist control (S628) when the first        non-holding condition is determined to be satisfied (S626: Yes),        and    -   during a performance of the lane changing assist control,    -   warn the driver (S622) by means of at least one of sound, an        indication, and vibration when the second non-holding condition        is determined to be satisfied (S618: Yes), whereas    -   continue the lane changing assist control until a completion        condition of the lane changing assist control becomes satisfied        (S620: Yes) regardless of the non-holding duration time.

The first invention apparatus comprises the lane recognition means, thesteering assist control means, the non-holding detection means, and thenon-holding determination means.

The lane recognition means recognizes the lane and acquires the laneinformation including the relative positional relationship of thevehicle with respect to the lane. The lane is a region defined by whitelines, for example. Therefore, the relative positional relationship ofthe vehicle with respect to the lane can be acquired by recognizing thelane.

The steering assist control means performs the lane tracing assistcontrol (LTA) and the lane changing assist control (LCA).

The LTA is a control to assist (support) the driver with the steeringoperation by changing the steered angle of the steered wheel of thevehicle such that the traveling position of the vehicle is kept at thepredetermined position in the lane in the lane width direction based onthe lane information. It should be noted that “the predeterminedposition in the lane width direction” is a position offset from a centerposition in the lane in the lane width direction toward the lane widthdirection by a predetermined distance with a value of more than or equalto zero and that is a position enabling the vehicle not to deviate fromthe lane, provided that the traveling position of the vehicle ispositioned at this position.

The LCA is a control to assist the driver with the steering operation bychanging the steered angle of the steered wheel of the vehicle such thatthe vehicle changes the lane from the original lane on which the vehicleis currently traveling to the target lane adjacent to the original lanebased on the lane information.

The non-holding detection means detects the non-holding state which is astate where the driver of the vehicle is not holding a steering wheel.

The non-holding determination means determines whether or not the firstnon-holding condition that the non-holding duration time which is “atime for which the non-holding state is continuing during a performanceof the LTA or the LCA” is more than or equal to the predetermined firsttime is satisfied and whether or not the second non-holding conditionthat the non-holding duration time is more than or equal to thepredetermined second time shorter than the first time is satisfied. Itshould be noted that each of the first time and the second time may be avariable relating to a vehicle speed.

In the first invention apparatus, the non-holding duration time ismeasured not only during a performance of the LTA, but also during aperformance of the LCA. Besides, when it is determined that the secondnon-holding condition is satisfied during a performance of the LCA, thesteering assist control means warns the driver by means of at least oneof sound, an indication, and vibration, whereas continues the LCA untilthe completion condition of the LCA becomes satisfied (that is, to theend) regardless of the non-holding duration time even though thenon-holding state continues after the warning. By measuring thenon-holding duration time also during a performance of the LCA andraising the warning when the second non-holding condition becomessatisfied as stated above, it becomes possible to urge the driver tohold the steering wheel also during a performance of the LCA. On theother hand, by not stopping but continuing the LCA to the end regardlessof the non-holding duration time (that is, for example, even though thenon-holding duration time increases as a result of the driver notholding the steering wheel in spite of the warning being raised during aperformance of the LCA), the LCA is prevented from being stopped in themidst of a performance thereof. Therefore, the vehicle can be preventedfrom deviating from the target lane due to the LCA being stopped, Hence,according to a configuration of the first invention apparatus, thevehicle can properly change the lane by the LCA while suppressing thedriver from overestimating the steering assist control by urging thedriver to hold the steering wheel during a performance of the steeringassist control.

In addition, in the first invention apparatus, when it is determinedthat the second non-holding condition becomes satisfied during aperformance of the LTA, the steering assist control means raises thewarning to the driver. The non-holding state is dissolved when thedriver holds the steering wheel upon this warning, Therefore, during aperformance of the LTA, a possibility that the non-holding statecontinues for more than or equal to the first time (a time longer thanthe second time) can be reduced. That is, a situation where “the firstnon-holding condition becomes satisfied and the LTA is stopped” can besuppressed from occurring. As a result, the LTA can be stably performed.

In another aspect of the steering assist apparatus of the presentinvention,

the steering assist control means (10, 20) is configured to start thelane changing assist control when a predetermined first startingcondition becomes satisfied (S612: Yes),

the first starting condition includes that the lane tracing assistcontrol is being performed, and

when the first starting condition becomes satisfied, the lane changingassist control is started in place of the lane tracing assist control.

According to this configuration, the first starting condition of the LCAdoes not become satisfied when the LTA is not being performed, andtherefore the LCA cannot be started. That is, when the LTA is stopped bybeing determined that the first non-holding condition becomes satisfiedduring a performance of the LTA, the LCA cannot be started. Therefore,when the driver demands a performance of the LCA, the driver comes tohold the steering wheel (strictly, comes to hold the steering wheel sothat the non-holding duration time does not become more than or equal tothe first time) in order for the LTA not to be stopped (that is, inorder for the first non-holding condition not to be satisfied). Hence,it becomes possible to urge the driver to hold the steering wheel duringa performance of the LTA.

In another aspect of the steering assist apparatus of the presentinvention,

the first starting condition further includes that the warning is notbeing raised.

According to this configuration, when the warning is being raised to thedriver as a result of the non-holding state continuing for more than orequal to the second time, the first starting condition of the LCA doesnot become satisfied even when the LTA is being performed and thereforethe LCA cannot be started. Therefore, when the driver demands aperformance of the LCA, the driver comes to hold the steering wheel(strictly, comes to hold the steering wheel so that the non-holdingduration time does not become more than or equal to the second time) inorder for the warning not to be raised (that is, in order for the secondnon-holding condition not to be satisfied). Hence, it becomes possibleto more surely urge the driver to hold the steering wheel during aperformance of the LTA.

A second steering assist apparatus of the present invention(hereinafter, may be referred to as a “second invention apparatus”) isapplied to a vehicle.

This second invention apparatus comprises;

lane recognition means (12) for recognizing a lane to acquire laneinformation including a relative positional relationship of the vehiclewith respect to the lane;

steering assist control means (10, 20) for performing a lane tracingassist control to assist a driver with a steering operation by changinga steered angle of a steered wheel of the vehicle such that a travelingposition of the vehicle is kept at a predetermined position in a lane ina lane width direction based on the lane information and a lane changingassist control to assist the driver with the steering operation bychanging the steered angle such that the vehicle changes a lane from anoriginal lane on which the vehicle is currently traveling to a targetlane adjacent to the original lane based on the lane information;

non-holding detection means (42) for detecting a non-holding state whichis a state where the driver of the vehicle is not holding a steeringwheel; and

non-holding determination means (S626) for measuring a non-holdingduration time which is a time for which the non-holding state iscontinuing during a performance of either the lane tracing assistcontrol or the lane changing assist control to determine whether or nota first non-holding condition that the non-holding duration time is morethan or equal to a predetermined first time (tu) is satisfied,

wherein,

the steering assist control means (10, 20) is configured to;

-   -   during a performance of the lane tracing assist control,    -   stop the lane tracing assist control (S628) when the first        non-holding condition is determined to be satisfied (S626: Yes),        and    -   during a performance of the lane changing assist control,    -   continue the lane changing assist control until a completion        condition of the lane changing assist control becomes satisfied        regardless of the non-holding duration time; and    -   not perform the lane tracing assist control (S628) when the        first non-holding condition is determined to be satisfied (S626:        Yes) at a point in time when the completion condition of the        lane changing assist control has been satisfied (S620: Yes).

In the second invention apparatus, during a performance of the LCA, thesteering assist control means continues the LCA until the completioncondition of the LCA becomes satisfied regardless of the non-holdingduration time. That is, during a performance of the LCA, “continuing theLCA to the end (until the LCA completion condition becomes satisfied)”is prioritized over “urging the driver to hold the steering wheel bystopping the LCA based on the non-holding duration time”. Besides, thesteering assist control means performs the LTA when it is determinedthat the first non-holding condition is not satisfied at a point in timewhen the LCA completion condition has been satisfied, whereas does notperform the LTA when it is determined that the first non-holdingcondition is satisfied at this point in time. In a latter case, thedriver comes to hold the steering wheel by noticing that the LTA has notbeen performed. Therefore, according to this configuration, it becomespossible to urge the driver to hold the steering wheel at a relativelyearly timing (that is, a timing at which the LCA completion conditionbecomes satisfied) when the first non-holding condition had beensatisfied during a performance of the LCA, while suppressing the vehiclefrom deviating from the target lane during a performance of the LCA.Hence, according to the second invention apparatus, the vehicle canproperly change the lane by the LCA while suppressing the driver fromoverestimating the steering assist control by urging the driver to holdthe steering wheel during a performance of the steering assist control.

In the above description, references used in the following descriptionsregarding embodiments are added with parentheses to the elements of thepresent invention, in order to assist in understanding the presentinvention. However, those references should not be used to limit thescope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a steering assist apparatus(hereinafter, also referred to as a “present embodiment apparatus”)according to an embodiment of the present invention.

FIG. 2 is a plan view showing each of attached positions of peripheralsensors and a camera sensor.

FIG. 3 is a diagram for describing lane related vehicle information.

FIG. 4 is a diagram for describing operations of a winker lever.

FIG. 5 is a diagram showing a target locus.

FIG. 6 is a flowchart showing a steering assist routine performed by CPUof driving support ECU of the present embodiment apparatus.

FIG. 7 is a flowchart showing a non-holding duration time measurementroutine performed by the CPU of the driving support ECU of the presentembodiment apparatus.

DESCRIPTION OF THE EMBODIMENT

Hereinafter, a description about a steering assist apparatus accordingto an embodiment of the present invention (hereinafter, also referred toas a “present embodiment apparatus”) will be made, referring figures.The present embodiment apparatus is applied to a vehicle (hereinafter,may be referred to as an “own vehicle” in order to distinguish it fromother vehicles), and comprises, as shown in FIG. 1, a driving supportECU 10, an electrically-driven power steering ECU 20, a meter ECU 30, asteering ECU 40, an engine ECU 50, a brake ECU 60, and a navigation ECU70. Hereinafter the driving support ECU 10 may be also referred to as a“DSECU 10”.

Each of the ECUs is an electric control unit comprising a microcomputeras a main part. Those ECUs are connected via CAN (Controller AreaNetwork) 100 so that the ECUs are capable of mutually transmitting andreceiving information. In the present specification, the microcomputerincludes CPU, ROM, RAM, a non-volatile memory, an interface IF, or thelike. The CPU is configured to realize/perform various functions byexecuting instructions (i.e., programs or routines) stored in the ROM.Some of those ECUs or all of those ECUs may be integrated to one ECU.

A plurality kinds of vehicle state sensors 80 for detecting states ofthe vehicle and a plurality kinds of driving operation state sensors 90for detecting driving operation states are connected to the CAN 100. Thevehicle state sensors 80 include a vehicle speed sensor for detecting atraveling speed of the vehicle, a front-rear G sensor for detecting anacceleration of the vehicle in a front-rear direction, a lateral Gsensor for detecting an acceleration of the vehicle in a lateraldirection, a yaw rate sensor for detecting a yaw rate of the vehicle,and the like.

The driving operation state sensors 90 include an acceleration operationamount sensor for detecting an operation amount of an accelerator pedal,a brake operation amount sensor for detecting an operation amount of abrake pedal, a brake switch for detecting whether or not a brake pedalis operated, a steering angle sensor for detecting a steering angle, asteering torque sensor for detecting a steering torque, a shift positionsensor for detecting a shift position of a gear, and the like.

Information detected by the vehicle state sensors 80 and the drivingoperation state sensors 90 (referred to as a “sensor information”) istransmitted to the CAN 100. Each of the ECUs can use the sensorinformation transmitted to the CAN 100. It should be noted that thesensor information is information of sensors connected to a specific ECUand may be transmitted to the CAN 100 from that specific ECU.

The DSECU 10 is a central control apparatus to perform various drivingsupports for the driver, and performs a lane changing assist control(LCA), a lane tracing assist control (LTA), and an adaptive cruisecontrol (ACC). As shown in FIG. 2, a front center peripheral sensor11FC, a front right peripheral sensor 11FR, a front left peripheralsensor 11FL, a rear right peripheral sensor 11RR, and a rear leftperipheral sensor 11RL are connected to the DSECU 10. Each of theperipheral sensors 11FC, 11FR, 11FL, 11RR, 11RL is a radar sensor.Although these sensors have different detection regions, they basicallyhave same configurations with each other. Hereinafter, when there is noneed to distinguish each of the peripheral sensors 11FC, 11FR, 11FL,11RR, 11RL from each other, they are combined to be called a peripheralsensor 11. It should be noted that the LCA and the LTA are controls forassisting steering operations of the driver, and therefore the LCA andthe LTA are combined to be called a “steering assist control”.

The peripheral sensor 11 comprises a radar transmission/reception partand a signal processing part (illustration omitted). The radartransmission/reception part emits an electric wave in a millimeterwaveband (hereinafter, referred to as a “millimeter wave”), and receivesa millimeter wave (i.e., a reflected wave) reflected from athree-dimensional object which is present in the emitted area (forexample, another vehicle, a pedestrian, a bicycle, a building, and thelike). The signal processing part acquires information (hereinafter,referred to as “peripheral information”) indicating a distance betweenthe own vehicle and the three-dimensional object, a relative speedbetween the own vehicle and the three-dimensional object, a relativeposition (direction) of the three-dimensional object with respect to theown vehicle, and the like every time a predetermined interval elapses toprovide the DSECU 10 with the acquired information. The peripheralinformation enables to detect a front-rear direction component and alateral direction component of the distance between the own vehicle andthe three-dimensional object as well as the front-rear directioncomponent and the lateral direction component of the relative speedbetween the own vehicle and the three-dimensional object.

As shown in FIG. 2, the front center peripheral sensor 11FC is providedat a front center part of a vehicle body, and detects athree-dimensional object present in a front region of the own vehicle.The front right peripheral sensor 11FR is provided at a front rightcorner part of the vehicle body, and mainly detects a three-dimensionalobject present in a front right region of the own vehicle. The frontleft peripheral sensor 11FL is provided at a front left corner part ofthe vehicle body, and mainly detects a three-dimensional object presentin a front left region of the own vehicle. The rear right peripheralsensor 11RR is provided at a rear right corner part of the vehicle body,and mainly detects a three-dimensional object present in a rear rightregion of the own vehicle. The rear left peripheral sensor 11RL isprovided at a rear left corner part of the vehicle body, and mainlydetects a three-dimensional object present in a rear left region of theown vehicle.

Besides, a camera sensor 12 is connected to the DSECU 10. The camerasensor 12 comprises a camera part and a lane recognition part foranalyzing an image data acquired by the camera part photographing torecognize a white line on a road. The camera sensor 12 (the camera part)photographs a scenery in front of the own vehicle. The camera sensor 12(the lane recognition part) provides the DSECU with informationregarding the recognized white line every time a predeterminedcalculation interval elapses.

The camera sensor 12 is configured to recognize a lane indicating aregion defined by white lines and detect, based on a positionalrelationship between the white lines and the own vehicle, a relativepositional relationship of the own vehicle with respect to the lane.Here, a position of the own vehicle means a position of a center ofgravity of the own vehicle. However, the position of the own vehicle maybe a center position of the own vehicle in a plan view. Besides, alateral position of the own vehicle which will be described later meansa position of the center of gravity of the own vehicle in a lane widthdirection, a lateral speed of the own vehicle means a speed of thecenter of gravity of the own vehicle in a lane width direction, and alateral acceleration of the own vehicle means an acceleration of thecenter of gravity of the own vehicle in a lane width direction. Thesevalues can be calculated based on the relative positional relationshipbetween the white lines detected by the camera sensor 12 and the ownvehicle.

As shown in FIG. 3, the camera sensor 12 determines a lane center lineCL which is a center position in a width direction of left and rightwhite lines WL of the lane on which the own vehicle is traveling. Thislane center line CL is used as a target traveling line in the LTA whichwill be described later. Further, the camera sensor 12 calculates acurvature Cu of a curve of the lane center line CL. It should be notedthat although the target traveling line is the lane center line CL inthe present embodiment, a line offset from the lane center line CL by apredetermined distance in the lane width direction may be adopted as thetarget traveling line.

In addition, the camera sensor 12 calculates a position and a directionof the own vehicle on the lane defined by the left and right white linesWL. For example, as shown in FIG. 3, the camera sensor 12 calculates adistance Dy [m] between a center-of-gravity point P of the own vehicle Cand the lane center line CL in the lane width direction, that is, adistance Dy by which the own vehicle C is deviated from the lane centerline CL in the lane width direction. Hereinafter, the distance Dy isreferred to as a lateral deviation Dy. Besides, the camera sensor 12calculates an angle θy [rad] formed by a direction of the lane centerline CL and a direction in which the own vehicle C is oriented.Hereinafter, the angle θy is referred to as a yaw angle θy. When thelane is curved, the lane center line CL is also curved, and thereforethe yaw angle θy in this case means an angle by which a direction inwhich the own vehicle C is oriented is deviated from this curved lanecenter line CL. Hereinafter, information (Cu, Dy, θy) showing thecurvature Cu, the lateral deviation Dy, and the yaw angle θy is referredto as a lane related vehicle information. It should be noted that leftand right directions with respect to the lane center line CL regardingthe lateral deviation Dy and the yaw angle θy are distinguished bypositive and negative signs. In addition, directions toward which a roadis curved (left and right) regarding the curvature Cu are distinguishedby positive and negative signs.

Further, the camera sensor 12 provides the DSECU 10 with informationregarding white lines of not only the lane of the own vehicle but alsothe adjacent lane, the information including a type of a white linedetected (a solid line, a broken line), a distance between adjacent leftand right white lines (a width of a lane), a shape of a white line, andthe like every time the predetermined calculation interval elapses. Whenthe white line is a solid line, it is prohibited for the own vehicle tochange a lane by striding over that white line. On the other hand, whenthe white line is a broken line (a white line formed intermittently at aconstant interval), it is permitted for the own vehicle to change a laneby striding over that white line. The lane related vehicle information(Cu, Dy, θy) and the information regarding white lines are combined tobe called a lane information.

It should be noted that although the camera sensor 12 calculates thelane related vehicle information (Cu, Dy, θy) in the present embodiment,the DSECU 10 may acquire the lane information instead by analyzing theimage data output by the camera sensor 12.

As shown in FIG. 1, a buzzer (a warning sound generating apparatus, awarning apparatus) 13 is connected to the DSECU 10. The buzzer 13 soundswhen receiving a sounding buzzer signal from the DSECU 10. The DSECU 10sounds the buzzer 13 in cases when notifying the driver of a drivingassist state, warning (alerting) the driver, and so on.

Besides, in place of or in addition to the buzzer 13, a vibrator (awarning apparatus) to transmit a warning (alerting) vibration to thedriver may be provided. For example, the vibrator is provided at asteering wheel and/or a seat and warns the driver through the vibrationof the steering wheel and/or the seat. Further, in place of or inaddition to the buzzer 13, an indicator (a warning apparatus) toindicate a message of warning (alerting) to the driver may be provided.

The DSECU 10 performs the ACC, the LTA, and the LCA based on thefollowing information such as the peripheral information provided by theperipheral sensor 11, the lane information acquired based on a whiteline recognition by the camera sensor 12, the vehicle state detected bythe vehicle state sensor 80, the driving operation states detected bythe driving operation state sensor 90, and the like.

A setting operation device 14 operated by the driver is connected to theDSECU 10. The setting operation device 14 is a device to performsettings and the like of whether or not to perform each of the ACC, LTA,and the LCA. The DSECU 10 inputs a setting signal of the settingoperation device 14 to determine whether or not to perform each of thecontrols. The setting operation device 14 is automatically set in such amanner that the LTA and the LCA are not to be performed when aperformance of the ACC has not been selected. Besides, the settingoperation device 14 is automatically set in such a manner that the LCAis not to be performed when a performance of the LTA has not beenselected.

The electric power steering ECU 20 is a control apparatus of an electricpower steering apparatus. Hereinafter, the electric power steering ECU20 is referred to as an EPS⋅ECU (Electric Power Steering ECU) 20. TheEPS⋅ECU 20 is connected to a motor driver 21. The motor driver 21 isconnected to a steered motor 22. The steered motor 22 is incorporatedinto a non-illustrated steering mechanism of the vehicle including “thesteering wheel, a steering shaft coupled to the steering wheel, asteering gear mechanism, and the like”. The EPS⋅ECU 20 detects asteering torque which the driver input to a steering wheel (illustrationomitted) by using a steering torque sensor arranged at a steering shaft.The EPS⋅ECU 20 controls an electric conduction of the motor driver 21based on the detected steering torque and drives the steered motor 22.When the steered motor 22 is driven, a steered angle of anon-illustrated steered wheel of the own vehicle is changed (the steeredwheel is steered). A steering torque is applied to the steeringmechanism by driving this assisting motor, assisting the steeringoperation of the driver.

Besides, when the EPS⋅ECU 20 receives a steering instruction from theDSECU 10 via the CAN 100, the EPS⋅ECU 20 drives the steered motor 22with a control amount specified by the steering instruction to generatea steering torque. This steering torque is different from the steeringassist torque applied in order to lighten the aforementioned steeringoperation (a steering wheel operation) by the driver, but is applied tothe steering mechanism by the steering instruction from the DSECU 10without the steering operation by the driver. This torque changes thesteered angle of the steered wheel of the own vehicle (the steered wheelis steered).

It should be noted that when a steering torque by a steering wheeloperation by the driver is detected and this steering torque is largerthan a threshold, even when the EPS⋅ECU 20 receives a steeringinstruction from the DSECU 10, the EPS⋅ECU 20 prioritize the steeringwheel operation by the driver and generate the steering assist torque tolighten this operation.

The meter ECU 30 is connected to an indicator 31 and left and rightwinkers 32. The left and right winkers 32 are winker lamps and may alsobe called turn lamps. The indicator 31 is, for example, a multiinformation display provided at a front of a driver's seat and indicatesvarious types of information in addition to measured values such as avehicle speed and the like by a meter. For instance, when receiving anindication instruction corresponding to a driving assist state from theDSECU 10, the meter ECU 30 indicates an image designated by theindication instruction on the indicator 31. It should be noted that ahead-up display (illustration omitted) may be adopted as the indicator31 in place of or in addition to the multi information display.

The meter ECU 30 comprises a winker driving circuit (illustrationomitted). When the meter ECU 30 receives a winker blinking instructionvia the CAN 100, the meter ECU 30 blinks one of the winkers 32corresponding to a direction/side (right or left) designated by thewinker blinking instruction. Hereinafter, one of the winkers 32 may bealso simply referred to as “the winker 32”. While blinking the winker32, the meter 30 transmits winker blinking information indicating thatthe winker 32 is blinking to the CAN 100. Thereby, other ECUs can graspa blinking state of the winker 32.

The steering ECU 40 is connected to a winker lever 41 and a non-holdingsensor 42. The winker lever 41 is an operation device to operate (blink)the winkers 32 and is provided at a steering column. The winker lever 41is provided in a revolvable way with two steps of operation strokesaround a spindle for each of a counterclockwise operation direction anda clockwise operation direction.

The winker lever 41 in the present embodiment also functions as anoperation device with which the driver requests the LCA. As shown inFIG. 4, the winker lever 41 is configured to be selectively operatable,for each of the counterclockwise operation direction and the clockwiseoperation direction around the spindle O, among a first stroke positionP1L (P1R) which is a position to which the winker lever 41 is revolvedfrom a neutral position PN by a first angle θW1 and a second strokeposition P2L (P2R) which is a position to which the winker lever 41 isrevolved from the neutral position PN by a second angle θW2 (>θW1). In acase where the winker lever 41 is shifted by a lever operation by thedriver to the first stroke position P1L (P1R), the winker lever 41 isconfigured to move back to the neutral position PN once an operationforce on the winker lever 41 by the driver is released. Further, in acase where the winker lever 41 is shifted by the lever operation by thedriver to the second stroke position P2L (P2R), the winker lever 41 isconfigured to be retained at the second stroke position P2L (P2R) by alock mechanism even when the operation force on the winker lever 41 isreleased. In addition, when the winker lever 41 which is in a state ofbeing retained at the second stroke position P2L (P2R) is moved back tothe neutral position PN by the steering wheel rotating in an oppositedirection or when the driver performs an operation to move the winkerlever 41 back toward a neutral position direction, the winker lever 41is configured to move back to the neutral position PN by the lockmechanism being unlocked.

The winker lever 41 comprises a first switch 411L (411R) which is turnedon (generates an on signal) only when a position thereof is at the firststroke position P1L (P1R) and a second switch 412L (412R) which isturned on (generates an on signal) only when a position thereof is atthe second stroke position P2L (P2R).

The steering ECU 40 detects an operation state of the winker lever 41based on whether or not there is the on signal from the first switch411L (411R) or the second switch 412L (412R). The steering ECU 40transmits to the meter ECU 30 the winker blinking instruction includinginformation indicating an operation direction (left or right) of thewinker lever 41 for each of the cases where the winker lever 41 isshifted to the first stroke position P1L (P1R) and the winker lever 41is shifted to the second stroke position P2L (P2R).

In addition, when the steering ECU 40 detects that the winker lever 41has been successively retained at the first stroke position P1L (P1R)for more than or equal to a predetermined set time (a lane changingrequest confirmation time: 1 sec, for instance), the steering ECU 40outputs to the DSECU 10 an LCA request signal including informationindicating the operation direction (left or right) of the winker lever41. Therefore, when the driver demands a performance of the LCA duringdriving, the driver may shift the winker lever 41 to the first strokeposition P1L (P1R) in a lane changing direction and retain that statefor more than or equal to the set time. Hereinafter, an operationdescribed above is referred to as an LCA request operation.

It should be noted that the winker lever 41 is used as an operationdevice with which the driver requests the LCA in the present embodiment.However, a dedicated LCA request operation device may be provided at thesteering wheel and the like instead.

The non-holding sensor 42 is a capacitance sensor provided inside thesteering wheel. The non-holding sensor 42 detects a state where thedriver is not holding the steering wheel (hereinafter, also referred toas a “non-holding state”) by detecting a capacitance of when the driveris holding the steering wheel and a capacitance of when the driver isnot holding the steering wheel. When the non-holding sensor 42 detectsthe non-holding state, the non-holding sensor 42 transmits to the DSECU10 via the CAN 100 a non-holding detection signal indicating that thenon-holding state is occurring.

When the transmission of the non-holding detection signal from thenon-holding sensor 42 is started, the DSECU 10 activates a count timerto (an initial value: zero) to start counting up a time for which thenon-holding detection signal is transmitted. This counting up isperformed only while the steering assist control (LCA, LTA) is beingperformed. That is, the DSECU 10 does not perform the counting up whilethe steering assist control is not being performed even when thenon-holding detection signal is transmitted from the non-holding sensor42.

When the transmission of the non-holding detection signal is stopped(that is, when the driver holds the steering wheel), the DSECU 10 resetsa value of the count timer tn. That is, the value of the count timer tnindicates “a time for which the non-holding state is continuing during aperformance of the steering assist control”. Hereinafter, this time isalso referred to as a “non-holding duration time”. On the other hand,when the steering assist control is stopped in the midst of thetransmission of the non-holding detection signal (that is, in the midstof counting up), the DSECU 10 does not reset the value of the counttimer tn but retains a value of a point in time when the steering assistcontrol has been stopped. This value of the count timer tn is retaineduntil the transmission of the non-holding detection signal is stopped(that is, until a value of the count timer tn is reset). Besides, thevalue of the count timer tn is reset at a point in time when an engineswitch is turned off. It should be noted that the capacitance sensor isused as the non-holding sensor 42 in the present embodiment. However, asteering torque sensor may be used for instance instead of thecapacitance sensor. Alternatively, a configuration where a camera tophotograph the driver is provided in a vehicle cabin and the non-holdingstate is detected based on an image photographed by the camera may beadopted.

It should be noted that the DSECU 10 does not measure the non-holdingduration time by the types of the steering assist control, but measuresthe non-holding duration time regardless of the types of the steeringassist control during a period of the steering assist control beingperformed. That is, even when the types of the steering assist controlis switched (namely, even when the steering assist control is switchedfrom the LTA to the LCA or vice versa) in the midst of the DSECU 10measuring the non-holding duration time, the DSECU 10 continues tomeasure the non-holding duration time without resetting it.

Referring back to FIG. 1, the engine ECU 50 is connected to an engineactuator 51. The engine actuator 51 includes actuators to change adriving state of an internal combustion engine 52. The engine ECU 50 canchange torque which the internal combustion engine 52 generates bydriving the engine actuator 51. Thereby, the engine ECU 50 can control adriving force of the own vehicle so as to change an acceleration state(an acceleration rate).

The brake ECU 60 is connected to a brake actuator 61. The brake actuator61 adjusts, in response to an instruction from the brake ECU 60, anhydraulic pressure that is supplied to a wheel cylinder which is builtin the brake caliper 62 b. Thereby, the brake actuator 61 presses abrake pad onto the brake disc 62 a to generate a friction braking force.Accordingly, the brake ECU 60 can control a braking force of the ownvehicle to change a deceleration state (a deceleration rate) bycontrolling the brake actuator 61.

The navigation ECU 70 is connected to a GPS receiver 71, a map database72, a touch panel (a touch-screen display) 73, and so on. The GPSreceiver 71 receives a GPS signal to detect a current position of theown vehicle. The map database 72 stores map information etc. Thenavigation ECU 70 identifies the current position of the own vehiclebased on the GPS signal, and performs various types of processing basedon the own vehicle position and on the map information etc. stored inthe map database 72 to perform a route guidance using the touch panel73.

The map information stored in the map database 72 includes roadinformation. The road information includes parameters representing aposition and a shape of a road (for example, a curvature radius of aroad, a curvature, a lane width of a road, the number of lanes, aposition of a center line of each lane, and the like). In addition, theroad information includes road types information etc. which enables todistinguish whether or not a road is a highway (a road exclusively usedby vehicles).

<Control Processing Performed by the DSECU 10>

Subsequently, control processing performed by the DSECU 10 will bedescribed. The DSECU 10 performs the ACC, the LTA, and the LCA.Therefore, these controls will be described first.

[ACC (Adaptive Cruise Control)]

The ACC performs following controls based on the peripheral information.That is, in a case when there exists a preceding vehicle traveling rightahead the own vehicle, the ACC makes the own vehicle trail the precedingvehicle, maintaining an inter-vehicular distance between the precedingvehicle and the own vehicle at a predetermined distance, and in a casewhen there does not exist such a preceding vehicle, the ACC makes theown vehicle travel at a constant speed set in advance. The ACC itself iswell known (for example, refer to Japanese Patent Applications Laid-Open(kokai) No. 2014-148293 and No. 2006-315491, and Japanese Patents No.4172434, and No. 4929777 and so on.) Therefore, a simple descriptionwill be made below.

When the ACC is being requested by an operation of the operation device14, the DSECU 10 performs the ACC. When the ACC is being requested, theDSECU 10 selects a trailing target vehicle based on the peripheralinformation provided from the peripheral sensor 11. For example, theDSECU 10 determines whether or not there exists another vehicle within apredetermined trailing target vehicle area.

When the other vehicle has been present within the trailing targetvehicle area over more than or equal to a predetermined time, the DSECU10 selects this other vehicle as a trailing target vehicle, and sets atarget acceleration in such a manner that the own vehicle trails thetrailing target vehicle, maintaining a predetermined inter-vehiculardistance to the trailing target vehicle. On the other hand, when theother vehicle is not present within the trailing target vehicle area,the DSECU 10 sets a target acceleration based on the set vehicle speedand the detected vehicle speed (the vehicle speed detected by thevehicle speed sensor) in such a manner that the vehicle speed of the ownvehicle coincides with the set vehicle speed.

The DSECU 10 controls the engine actuator 51 using the engine ECU 50,and when necessary, controls the brake actuator 61 using the brake ECU60 so that the acceleration of the own vehicle coincides with the targetacceleration. It should be noted that when an acceleration operation isperformed by the driver during the ACC and as a result a requestedacceleration based on this acceleration operation has exceeded thetarget acceleration, the acceleration operation is prioritized(acceleration override) and the ACC is not performed. The ACC isautomatically resumed after the acceleration override. This is a summaryof the ACC.

[LTA (Lane Tracing Assist Control)]

The LTA is a control to support the steering operation (the lane tracingoperation) by the driver by adding the steering torque to the steeringmechanism so that a position of the own vehicle is kept nearby (in thevicinity of) a target traveling line in a “lane on which the own vehicleis traveling”. The LTA itself is well known (for example, refer toJapanese Patent Applications Laid-Open (kokai) No. 2008195402, No.2009-190464, No. 2010-6279, and Japanese Patent No. 4349210, and so on).Therefore, a simple description will next be made below.

The DSECU 10 starts the LTA when an LTA starting condition is satisfied.For example, the LTA starting condition is satisfied when followingconditions are all satisfied.

1. A performance of the LTA has been selected with the setting operationdevice 14.

2. The ACC is being performed.

3. The while lines have been able to be recognized by the camera sensor12.

4. A value of the count timer to has been reset (described later).

It should be noted that the LTA starting condition is not limited to theconditions above but can be set arbitrarily.

When the LTA starting condition is satisfied, the DSECU 10 calculates atarget steered angle θlta* based on the aforementioned lane relatedvehicle information (Cu, Dy, θy) every time the predeterminedcalculation interval elapses to output to the EPS⋅ECU 20 an instructionsignal indicating the target steered angle θlta*. The EPS⋅ECU 20controls driving of the steered motor 22 so that the steered anglefollows the target steered angle θlta*.

Besides, when the own vehicle comes into a situation where the ownvehicle deviates out of the lane, the DSECU 10 raises a lane deviationwarning by sounding the buzzer 13 and so on. This is a summary of theLTA.

[LCA (Lane Changing Assist Control)]

The LCA is a control to assist the steering operation (the lane changingoperation) by the driver by applying a steering torque to the steeringmechanism so that the own vehicle moves to an adjacent lane from a laneon which the own vehicle is currently traveling while monitoring aperiphery of the own vehicle after being determined that a safe lanechange is possible as a result of monitoring the periphery of the ownvehicle. The LCA itself is well known (for example, refer to JapanesePatent Applications Laid-Open (kokai) No. 2016-207060, No. 2017-74823,and so on). Therefore, a simple description will next be made below.

The DSECU 10 starts the LCA when an LCA starting condition is satisfied.For example, the LCA starting condition is satisfied when followingconditions are all satisfied.

1. The LCA request operation (the LCA request signal) is detected.

2. A performance of the LCA has been selected with the setting operationdevice 14.

3. The LTA is being performed.

4. A non-holding warning has not been raised during the performance ofthe LTA (described later).

5. A white line positioned in the winker operation direction (a whiteline positioned between the original lane and the target lane) is abroken line.

6. A determination result of whether or not the LCA can be performedaccording to the monitoring of the periphery is positive (That is, basedon the peripheral information acquired by the peripheral sensor 11, noobstacles (other vehicles etc.) which may interfere with the lane changehas been detected, and it has been determined that a safe lane change ispossible).

7. A road is a highway (a road exclusively used by vehicles). In otherwords, the road types information acquired from the navigation ECU 70indicates that a road is a highway.

8. A vehicle speed of the own vehicle is in an LCA permission vehiclespeed range where the LCA is permitted. For example, the condition 8 issatisfied when it is estimated that an inter-vehicular distance betweenthe own vehicle and an other vehicle traveling on the target lane afterthe lane change is properly ensured based on a relative speed betweenthe own vehicle and the other vehicle.

It should be noted that the LCA starting condition is not limited to theconditions above but can be set arbitrarily.

When the LCA starting condition is satisfied, the DSECU 10 calculates atarget locus function y(t) to determine a target locus of the ownvehicle. The target locus is a locus on which the own vehicle moves fromthe lane on which the own vehicle is currently traveling (that is, theoriginal lane) to a central position (referred to as a final targetlateral position) in the width direction of the lane adjacent to theoriginal lane and is positioned in an LCA requested direction (that is,the target lane), taking a target-time-required-for-a-lane-change. Thetarget locus has a shape shown in FIG. 5, for example.

The target locus function y(t) is defined by using an elapsed time tfrom an LCA starting point in time (that is, a point in time when theLCA starting condition has been satisfied) as a variable. The targetlocus function y(t) calculates a target value of the lateral position(that is, a target lateral position) of the own vehicle corresponding tothe elapsed time t on a basis of the lane center line CL of the originallane. Here, the lateral position of the own vehicle means a position ofthe center of gravity of the own vehicle in the lane width direction(that is, the lateral direction) on the basis of the lane center lineCL.

The target-time-required-for-a-lane-change is set in such a manner thatthe target-time-required-for-a-lane-change may vary in proportion to adistance necessary to move the own vehicle in the lateral direction froman initial lateral position which is a starting position of the LCA (alateral position of the own vehicle at the LCA starting point in time)to the final target lateral position. Hereinafter, this distance isreferred to as a “necessary lateral distance”.

The target locus function is determined based on a state of the ownvehicle at the LCA starting point in time, a target state of the ownvehicle at an LCA completion point in time, and thetarget-time-required-for-a-lane-change. Here, “the state of the ownvehicle at the LCA starting point in time” includes “the initial lateralposition, a lateral speed at the initial lateral position, and a lateralacceleration at the initial lateral position of the own vehicle”.Besides, “the target state of the own vehicle at the LCA completionpoint in time” includes “the final target lateral position, a lateralspeed at the final target lateral position (that is, zero), and alateral acceleration at the final target lateral position (that is,zero) of the own vehicle”. The target locus determined in this way has ashape on which the own vehicle can smoothly travel to the final targetlateral position.

The DSECU 10 stores this target locus function y(t) and performs thesteering control based on the target locus function y(t) until the LCAfinishes. Specifically, the DSECU 10 calculates the target steered angleθlca* by performing following processing every time the predeterminedcalculation interval elapses. That is, the DSECU 10 calculates a targetlateral position y*, a target lateral speed vy*, and a target lateralacceleration ay* at a current point in time based on the target locusfunction y(t) and the elapsed time t. Subsequently, the DSECU 10calculates a target yaw angle θy*, a target yaw rate γ*, and a targetcurvature Cu* at the current point in time based on the vehicle speed v,the target lateral speed vy*, and the target lateral acceleration ay* atthe current point in time. Thereafter, the DSECU 10 calculates thetarget steered angle θlca* based on the target lateral position y*, thetarget yaw angle θy*, the target yaw rate γ*, and the target curvatureCu*. It should be noted that the LCA finishes when an LCA completioncondition that the lateral position of the own vehicle reaches the finaltarget lateral position is satisfied.

Upon a calculation of the target steered angle θlca*, the DSECU 10outputs to the EPS⋅ECU 20 an instruction signal indication the targetsteered angle θlca*. The EPS⋅ECU 20 controls driving of the steeredmotor 22 so that the steered angle follows the target steered angleθlca*. This is a summary of the LCA.

It should be noted that the present embodiment apparatus performs acontrol to assist (support) the steering operation by the driver.Therefore, when performing the steering assist control (LTA, LCA), theDSECU 10 generates a steering force for the steering assist control suchthat the steering wheel operation by the driver is prioritized. Thereby,the driver can drive the own vehicle in a direction to which the driverintends to drive with his/her own steering wheel operation.

Next, processing by the DSECU 10 corresponding to the non-holdingduration time will be described. The DSECU 10 determines whether or notthe non-holding duration time (a time for which the non-holding state iscontinuing during a performance of the steering assist control) is morethan or equal to a non-holding warning time tw set in advance (10seconds, for example) every time the predetermined calculation intervalelapses. When it is determined that the non-holding duration time ismore than or equal to the non-holding warning time tw, the DSECU 10determines that a non-holding-condition-for-warning is satisfied andsounds the buzzer 13 to warn (alert) the driver. This warning isreferred to as a non-holding warning. It should be noted that thenon-holding warning time tw may be a variable which decreases as thevehicle speed increases. Besides, the “non-holding warning time tw”corresponds to one example of a “second time”, and the“non-holding-condition-for-warning” corresponds to one example of a“second non-holding condition”.

Besides, the DSECU 10 determines whether or not the non-holding durationtime is more than or equal to a non-holding upper limit time tu set inadvance every time the predetermined calculation interval elapses. Thisnon-holding upper limit time tu is set to be a larger value than thenon-holding warning time tw (13 seconds, for example). When it isdetermined that the non-holding duration time is more than or equal tothe non-holding upper limit time tu, the DSECU 10 determines that anon-holding-condition-for-turning-control-off is satisfied. When it isdetermined that the non-holding-condition-for-turning-control-off issatisfied during a performance of the LTA, the DSECU 10 stops the LTA.

Now, the aforementioned condition 4 of the LTA starting condition willbe described. When it is determined that thenon-holding-condition-for-turning-control-off is satisfied and the LTAis stopped, the value of the count timer tn is not reset but the valueof a point in time when the LTA has been stopped is retained asmentioned above. Therefore, in order for the condition 4 of the LTAstarting condition to be satisfied, it is required for the driver tohold the steering wheel at least once after the LTA is stopped. In otherwords, the LTA is not to be resumed during a period where thenon-holding state is continuing after the LTA is stopped. When thedriver holds the steering wheel after the LTA is stopped, the value ofthe count timer tn is reset and thus the condition 4 becomes satisfied.A non-holding duration time after the LTA is resumed can be preciselymeasured by the value of the count timer tn being reset. It should benoted that when the LTA is performed for the first time after the engineswitch is turned on, the value of the count timer tn has been reset, andtherefore the condition 4 has been automatically satisfied. Hence, theDSECU 10 is configured not to confirm whether or not the condition 4 issatisfied in the aforementioned case.

In contrast, during a performance of the LCA, the DSECU 10 does not stopbut continues the LCA to the end regardless of the non-holding durationtime. Thereafter, the DSECU 10 determines whether or not the non-holdingduration time is more than or equal to the non-holding upper limit timetu at a point in time when the LCA completion condition has beensatisfied. When it is determined that the non-holding duration time isless than the non-holding upper limit time tu, the DSECU 10 determinesthat the non-holding-condition-for-turning-control-off is not satisfiedto perform the LTA. That is, the DSECU 10 resumes the LTA after the LCAis finished. On the other hand, when it is determined that thenon-holding duration time is more than or equal to the non-holding upperlimit time tu, the DSECU 10 determines that thenon-holding-condition-for-turning-control-off is satisfied not toperform (resume) the LTA. It should be noted that the non-holding upperlimit time tu may be a variable which decreases as the vehicle speedincreases. In addition, the “non-holding upper limit time tu”corresponds to one example of a “first time”, and the“non-holding-condition-for-turning-control-off” corresponds to oneexample of a “first condition”.

When it is determined that the non-holding-condition-for-warning issatisfied during a performance of the LTA, and the non-holding warningis raised, the condition 4 among the LCA starting condition becomesunsatisfied, and therefore the LCA starting condition becomesunsatisfied. Hence, the DSECU 10 does not start the LCA even when otherconditions (the condition 1 to 3 and the conditions 5 to 8) are allsatisfied. In addition, when it is determined that thenon-holding-condition-for-turning-control-off is satisfied during aperformance of the LTA and the LTA is stopped, the conditions 3 and 4among the LCA starting condition become unsatisfied, and therefore theLCA starting condition becomes unsatisfied. The DSECU 10 does not startthe LCA in this case as well. That is, in order for the LCA startingcondition to be satisfied, it is required for at least the LTA to bebeing performed in a state where “the non-holding warning is not beingraised” (that is, a state where the non-holding duration time is lessthan the non-holding warning time tw).

Subsequently, control processing performed by the DSECU 10 will bespecifically described, referring to FIG. 6 and FIG. 7. When an ignitionswitch is turned on, the DSECU 10 performs routines shown by flowchartsin FIG. 6 and FIG. 7 in parallel. It should be noted that hereinafter, astatus of the steering assist control (LTA, LCA) is referred to as a“steering assist control state”.

When the DSECU 10 starts processing from a step S600 in FIG. 6 after theignition switch is turned on, the DSECU 10 sets, at a step S602, thesteering assist control state to be an LTA⋅OFF state. Here, the LTA⋅OFFstate is a control state where the LTA is not being performed.

Next, the DSECU 10 proceeds to a step S604 to determine whether or notthe aforementioned LTA starting condition is satisfied. When it isdetermined that the LTA starting condition is not satisfied (S604: No),the DSECU 10 returns back to the step S602. The DSECU 10 repeatsprocessing of the steps 602 and 604 every time the predeterminedcalculation interval elapses until the LTA starting condition isdetermined to be satisfied.

When it is determined that the LTA starting condition is satisfied(S604: Yes) in the midst of the processing mentioned above, the DSECU 10proceeds to a step S606 to set the steering assist control state to bean LTA⋅ON state. Here, the LTA⋅ON state is a control state where the LTAis being performed. In other words, the DSECU 10 starts the LTA.

Subsequently, the DSECU 10 proceeds to a step S608 to read the counttimer tn. The count time tn is measured by the routine shown in FIG. 7.Therefore, hereinafter, a measurement with the count timer tn will bedescribed, referring to FIG. 7.

When the DSECU 10 starts processing from a step S700 in FIG. 7 after theignition switch is turned on, the DSECU 10 determines, at a step S702,whether or not the non-holding state is detected. When it is determinedthat the non-holding state is not detected (that is, the driver isholding the steering wheel), (step S702: No), the DSECU 10 proceeds to astep S706 to reset (zero clear) the value of the count timer tn, andtentatively terminates the routine of FIG. 7 at a step S710. The valueof the count timer tn has been set to zero at a point in time when theignition switch is turned on.

The DSECU 10 repeats the processing mentioned above every time thepredetermined calculation interval elapses. When it is determined thatthe non-holding state is detected at the step S702 (S702: Yes) in themidst of the processing, the DSECU 10 proceeds to a step 704 todetermine whether or not the steering assist control state is either theLTA⋅ON state or an LCA⋅ON state. Here, the LCA⋅ON state is a controlstate where the LCA is being performed. That is, the DSECU 10determines, at the step S704, whether or not the steering assist controlis being performed.

When it is determined that the steering assist control state is eitherthe LTA⋅ON state or an LCA⋅ON state (S704: Yes), the DSECU 10 proceedsto a step 708 to increase the value of the count timer tn by 1.Therefore, the value of the count timer tn indicates the non-holdingduration time. After finishing the processing of the step S708, theDSECU 10 tentatively terminates the routine of FIG. 7 at the step S710.

The DSECU 10 repeats the processing mentioned above every time thepredetermined calculation interval elapses. When it is determined thatthe steering assist control state is neither the LTA⋅ON state nor theLCA⋅ON state (that is, the steering assist control is not beingperformed) at the step S704 (S704: No) in the midst of the processing,the DSECU 10 tentatively terminates the routine of FIG. 7 at the stepS710. That is, when it is determined that the steering assist control isnot being performed, the DSECU 10 does not reset the value of the counttimer tn but retains the value of that point in time.

The DSECU 10 repeats the processing mentioned above every time thepredetermined calculation interval elapses. When it is determined thatthe non-holding state is not detected (that is, the driver is holdingthe steering wheel) at the step S702 (S702: No) in the midst of theprocessing, the DSECU 10 proceeds to the step S706 to reset the value ofthe count timer tn. That is, the value of the count timer tn retained atthe point in time when a “No” determination has been made at the stepS704 is reset.

The DSECU 10 repeats the processing mentioned above every time thepredetermined calculation interval elapses until the ignition switch isturned off. In this way, the non-holding duration time is measured.

Referring back to FIG. 6, when the DSECU 10 reads the count timer tn atthe step S608, the DSECU 10 proceeds to a step S610 to determine whetheror not the value of the count timer tn (that is, the non-holdingduration time) is more than or equal to the non-holding warning time tw.When it is determined that the non-holding duration time is less thanthe non-holding warning time tw (S610: No), the DSECU 10 determines thatthe non-holding-condition-for-warning is not satisfied and proceeds to astep S612.

The DSECU 10 determines, at the step S612, whether or not theaforementioned LCA starting condition is satisfied. When it isdetermined that the LCA staring condition is not satisfied (S612: No),the DSECU 10 returns to the step S606 to continue the LTA.

The DSECU 10 repeats the processing mentioned above every time thepredetermined calculation interval elapses. When it is determined thatthe LCA staring condition is satisfied (S612: Yes) in the midst of theprocessing, the DSECU 10 proceeds to the step S614 to set the steeringassist control state as the LCA-ON state. That is, the DSECU 10 startsthe LCA (performs the LCA in place of the LTA).

Subsequently, the DSECU 10 proceeds to a step S616 to read the counttimer tn. Thereafter, the DSECU 10 proceeds to a step S618 to determinewhether or not the value of the count timer tn (that is, the non-holdingduration time) is more than or equal to the non-holding warning time tw.At a point in time when it has been determined that the LCA startingcondition is satisfied at the step S612, tn<tw is satisfied at the stepS610, and therefore the non-holding duration time is less than thenon-holding warning time tw (S618: No). In this case, the DSECU 10proceeds to a step S620 to determine whether or not the aforementionedLCA completion condition is satisfied. At the point in time when it hasbeen determined that the LCA starting condition is satisfied at the stepS612, the LCA completion condition is not satisfied (S620: No). In thiscase, the DSECU 10 returns to the step S614 to continue the LCA.

The DSECU 10 repeats the processing mentioned above every time thepredetermined calculation interval elapses. When it is determined thatthe non-holding duration time has reached the non-holding warning timetw at the step S618 (S618: Yes) in the midst of the processing, theDSECU 10 determines that the non-holding-condition-for-warning issatisfied and at a step S622, sounds the buzzer 13 to raise thenon-holding warning (alerting) to the driver.

Thereafter, the DSECU 10 proceeds to the step S620 to determine whetheror not the LCA completion condition is satisfied. The DSECU 10 repeatsthe processing mentioned above every time the predetermined calculationinterval elapses. When it is determined that the LCA completioncondition is satisfied at the step S620 (S620: Yes) in the midst of theprocessing, the DSECU 10 proceeds to a step S626 to determine whether ornot the value of the count timer tn (that is, the non-holding durationtime) is more than or equal to the non-holding upper limit time tu.

When it is determined that the non-holding duration time is more than orequal to the non-holding upper limit time tu (in other words, when thenon-holding duration time has become more than or equal to thenon-holding upper limit time tu during a performance of the LCA), (S626:Yes), the DSECU 10 determines that thenon-holding-condition-for-turning-control-off is satisfied and proceedsto a step S628 to stop the LTA. That is, the DSECU 10 sets the steeringassist control state as the LTA⋅OFF state. At this time, the counting upof the count timer tn is stopped and the value of a point in time whenthe counting up is stopped is retained. After finishing the processingof the step S628, the DSECU 10 proceeds to a step S630 to tentativelyterminate the routine of FIG. 6.

On the other hand, when it is determined that the non-holding durationtime is less than the non-holding upper limit time tu (S626: No), theDSECU 10 returns to the step S606 to set the steering assist controlstate as the LTA⋅ON state. That is, the DSECU 10 finishes the LCA andresumes the LTA.

The DSECU 10 repeats the processing mentioned above every time thepredetermined calculation interval elapses. When it is determined thatthe non-holding duration time has reached the non-holding warning timetw at the step S610 (S610: Yes) in the midst of the processing, theDSECU 10 determines that the non-holding-condition-for-warning issatisfied to proceed to the step S624. At the step S624, the DSECU 10sounds the buzzer 13 to raise the non-holding warning (alerting) to thedriver.

Thereafter, the DSECU 10 proceeds to the step S626 to determine whetheror not the value of the count timer tn (the non-holding duration time)is more than or equal to the non-holding upper limit time tu. At a pointin time when it has been determined that the non-holding duration timehas reached the non-holding warning time tw at the step S610, thenon-holding duration time is less than the non-holding upper limit timetu (S626: No). In this case, the DSECU 10 determines that thenon-holding-condition-for-turning-control-off is not satisfied andreturns to the step S606 to continue the LTA.

The DSECU 10 repeats the processing mentioned above every time thepredetermined calculation interval elapses. When it is determined thatthe non-holding duration time has reached the non-holding upper limittime tu at the step S626 (S626: Yes) in the midst of the processing, theDSECU 10 determines that thenon-holding-condition-for-turning-control-off is satisfied and proceedsto the step S628 to stop the LTA. That is, the DSECU 10 sets thesteering assist control state as the LTA⋅OFF state. At this time, thecounting up of the count timer tn is stopped and the value of a point intime when the counting up is stopped is retained.

After finishing the processing of the step S628, the DSECU 10 proceedsto the step S630 to tentatively terminate the routine of FIG. 6.Thereafter, the DSECU 10 returns to the step S600 and repeats theprocessing from the step S602 every time the predetermined calculationinterval elapses until the ignition switch is turned off. It should benoted that when the non-holding-condition-for-warning becomes satisfied(S618: Yes) during a performance of the LCA, the non-holding warning israised at the step S622. When the driver comes to hold the steeringwheel as a result of the warning, the value of the count timer tn isreset (S702: No, S706). After that, when the LCA completion condition isnot satisfied (S620: No) and the non-holding-condition-for-warningbecomes satisfied (S618: Yes) as a result of the non-holding state againcontinuing, the non-holding warning is again raised at the step S622.That is, the non-holding warning during a performance of the LCA can beraised more than once. The non-holding warning is raised every time thenon-holding-condition-for-warning becomes satisfied. The same thing canbe said to the non-holding warning during a performance of the LTA.

Effects of the present embodiment apparatus will be described. In aprior art steering assist apparatus, the non-holding duration time ismeasured only during a performance of the LTA. Besides, during aperformance of the LTA, the prior art apparatus urges the driver to holdthe steering wheel by raising the non-holding warning when thenon-holding duration time becomes more than or equal to the non-holdingwarning time tw and urges the driver to hold the steering wheel bystopping the LTA when the non-holding duration time further increases tohave reached the non-holding upper limit time tu.

In contrast, in the present embodiment apparatus, the non-holdingduration time is measured not only during a performance of the LTA, butalso during a performance of the LCA. Besides, when it is determinedthat the non-holding-condition-for-warning is satisfied during aperformance of the LCA, the present embodiment apparatus raises thenon-holding warning, whereas continues the LCA until the LCA completioncondition becomes satisfied (that is, to the end) regardless of thenon-holding duration time even though the non-holding state continuesafter the non-holding warning. By measuring the non-holding durationtime also during a performance of the LCA and raising the warning whenthe non-holding-condition-for-warning becomes satisfied, it becomespossible to urge the driver to hold the steering wheel also during aperformance of the LCA, not only during a performance of the LTA. On theother hand, by not stopping but continuing the LCA to the end regardlessof the non-holding duration time (that is, for example, even though thenon-holding duration time increases as a result of the driver notholding the steering wheel in spite of the warning being raised during aperformance of the LCA), the LCA is prevented from being stopped in themidst of a performance thereof. Therefore, the vehicle can be preventedfrom deviating from the target lane due to the LCA being stopped. Hence,according to a configuration of the present embodiment apparatus, thevehicle can properly change the lane by the LCA while suppressing thedriver from overestimating the steering assist control by urging thedriver to hold the steering wheel during a performance of the steeringassist control.

In addition, in the present embodiment apparatus, the non-holdingduration time is not reset even when the types of the steering assistcontrol are switched from each other. Therefore, when the non-holdingstate had continued before the LTA is resumed (that is, during aperformance of the LCA) the non-holding duration time will be a sum of“the non-holding duration time during a performance of the LCA” and “thenon-holding duration time after the LTA is resumed”. According to thisconfiguration, the non-holding-condition-for-turning-control-off becomessatisfied at an early timing after the LTA is resumed. That is, the LTAis stopped at an early timing.

For example, when the non-holding state is detected during a performanceof the LCA and thereafter the LTA is resumed with the non-holding stateremaining continued, the LTA is stopped immediately after beingdetermined that the non-holding-condition-for-turning-control-offbecomes satisfied after the LTA is resumed. Hence, it becomes possibleto urge the driver to hold the steering wheel at an early timing and tomore surely suppress the driver from overestimating the steering assistcontrol.

Further, in the present embodiment apparatus, the conditions 3 and 4among the LCA starting condition do not become satisfied when the LTA isnot being performed, and therefore the LCA cannot be started. That is,when the LTA is stopped by being determined that thenon-holding-condition-for-turning-control-off becomes satisfied during aperformance of the LTA, the LCA cannot be started. Therefore, when thedriver demands a performance of the LCA, the driver comes to hold thesteering wheel (strictly, comes to hold the steering wheel so that thenon-holding duration time does not become more than or equal to thenon-holding upper limit time tu) in order for the LTA not to be stopped(that is, in order for the non-holding-condition-for-turning-control-offnot to be satisfied). Hence, it becomes possible to urge the driver tohold the steering wheel during a performance of the LTA.

Further, in the present embodiment apparatus, when it is determined thatthe non-holding-condition-for-warning becomes satisfied during aperformance of the LTA, the condition 4 among the LCA starting conditiondoes not become satisfied, and therefore the LCA cannot be started. Thatis, when the non-holding warning is being raised to the driver as aresult of the non-holding state continuing for more than or equal to thenon-holding warning time tw, the LCA cannot be started even when the LTAis being performed. Therefore, when the driver demands a performance ofthe LCA, the driver comes to hold the steering wheel (strictly, comes tohold the steering wheel so that the non-holding duration time does notbecome more than or equal to the non-holding warning time tw) in orderfor the non-holding warning not to be raised (that is, in order for thenon-holding-condition-for-warning not to be satisfied). Hence, itbecomes possible to more surely urge the driver to hold the steeringwheel during a performance of the LTA.

Further, in the present embodiment apparatus, during a performance ofthe LCA, the present embodiment apparatus continues the LCA until theLCA completion condition becomes satisfied regardless of the non-holdingduration time. That is, during a performance of the LCA, “continuing theLCA to the end (until the LCA completion condition becomes satisfied)”is prioritized over “urging the driver to hold the steering wheel bystopping the LCA based on the non-holding duration time”. Besides, thepresent embodiment apparatus determines whether or not thenon-holding-condition-for-turning-control-off is satisfied at a point intime when the LCA completion condition has been satisfied, and whendetermined to be satisfied, the LTA is not performed. In this case, thedriver comes to hold the steering wheel by noticing that the LTA has notbeen performed. Therefore, it becomes possible to urge the driver tohold the steering wheel at a relatively early timing (that is, a timingat which the LCA completion condition becomes satisfied) when thenon-holding-condition-for-turning-control-off had been satisfied duringa performance of the LCA, while suppressing the vehicle from deviatingfrom the target lane during a performance of the LCA.

Hence, according to the present embodiment apparatus, the vehicle canproperly change the lane by the LCA while suppressing the driver fromoverestimating the steering assist control by urging the driver to holdthe steering wheel during a performance of the steering assist control.

The steering assist apparatus according to the present embodiment hasbeen described. However, the present invention is not limited to theaforementioned embodiment and may adopt various modifications within ascope of the present invention.

For example, although the non-holding warning is raised when it isdetermined that the non-holding duration time has become more than orequal to the non-holding warning time tw in the present embodiment, thenon-holding warning may not be raised. That is, a followingconfiguration may be adopted, the configuration being a configurationwhere during a performance of the LTA, the DSECU 10 only determineswhether or not the non-holding-condition-for-turning-control-off issatisfied whereas during a performance of the LCA, the DSECU 10continues the LCA to the end (that is, until the LCA completioncondition becomes satisfied) regardless of the non-holding durationtime.

In addition, although the capacitance sensor is used as the non-holdingsensor 42 and the non-holding duration time is measured using thiscapacitance sensor in the present embodiment, the non-holding durationtime may be measured using a steering torque sensor or a camera insteadof the capacitance sensor.

Further, although the non-holding warning is raised by sounding thebuzzer 13 in the present embodiment, the non-holding warning may beraised by vibrating the steering wheel and/or the seat with a vibratorinstead of or in addition to sounding the buzzer 13. Alternatively, thenon-holding warning may be raised by indicating a warning message to thedriver on the indicator.

Further, in the present embodiment, the setting operation device 14 isautomatically set in such a manner that the LTA and the LCA are not tobe performed when a performance of the ACC has not been selected andthat the LCA is not to be performed when a performance of the LTA hasnot been selected. However, a configuration is not limited thereto. Forexample, the setting operation device 14 may be configured to be able toselect performance of the LTA and the LCA even when a performance of theACC has not been selected.

Further, although a lane recognized by the camera sensor 12 in thepresent embodiment, a configuration where, for example, a relativepositional relationship of the own vehicle with respect to a lane isdetected by the navigation ECU 70 may be adopted.

The invention claimed is:
 1. A steering assist apparatus applied to avehicle comprising; lane recognition means for recognizing a lane toacquire lane information including a relative positional relationship ofsaid vehicle with respect to said lane; steering assist control meansfor performing a lane tracing assist control to assist a driver with asteering operation by changing a steered angle of a steered wheel ofsaid vehicle such that a traveling position of said vehicle is kept at apredetermined position in a lane in a lane width direction based on saidlane information and a lane changing assist control to assist saiddriver with said steering operation by changing said steered angle suchthat said vehicle changes a lane from an original lane on which saidvehicle is currently traveling to a target lane adjacent to saidoriginal lane based on said lane information; non-holding detectionmeans for detecting a non-holding state which is a state where saiddriver of said vehicle is not holding a steering wheel; and non-holdingdetermination means for measuring a non-holding duration time which is atime for which said non-holding state is continuing during a performanceof either said lane tracing assist control or said lane changing assistcontrol to determine whether or not a first non-holding condition thatsaid non-holding duration time is more than or equal to a predeterminedfirst time is satisfied and whether or not a second non-holdingcondition that said non-holding duration time is more than or equal to apredetermined second time shorter than said first time is satisfied,wherein, said steering assist control means is configured to; during aperformance of said lane tracing assist control, warn said driver bymeans of at least one of sound, an indication, and vibration when saidsecond non-holding condition is determined to be satisfied; and stopsaid lane tracing assist control when said first non-holding conditionis determined to be satisfied, and during a performance of said lanechanging assist control, warn said driver by means of at least one ofsound, an indication, and vibration when said second non-holdingcondition is determined to be satisfied, whereas continue said lanechanging assist control until a completion condition of said lanechanging assist control becomes satisfied regardless of said non-holdingduration time.
 2. The steering assist apparatus according to claim 1,wherein, said steering assist control means is configured to start saidlane changing assist control when a predetermined first startingcondition becomes satisfied, said first starting condition includes thatsaid lane tracing assist control is being performed, and when said firststarting condition becomes satisfied, said lane changing assist controlis started in place of said lane tracing assist control.
 3. The steeringassist apparatus according to claim 2, wherein, said first startingcondition further includes that said warning is not being raised.
 4. Thesteering assist apparatus according to claim 1, wherein, said steeringassist control means is configured to; start said lane changing assistcontrol when a predetermined first starting condition becomes satisfied,when said first starting condition becomes satisfied, calculate a targetlocus function to determine a target locus which is a locus on whichsaid vehicle moves from said original lane to a predetermined positionof said target lane, taking a predetermined time, and perform said lanechanging assist control based on said target locus function.
 5. Asteering assist apparatus applied to a vehicle comprising; lanerecognition means for recognizing a lane to acquire lane informationincluding a relative positional relationship of said vehicle withrespect to said lane; steering assist control means for performing alane tracing assist control to assist a driver with a steering operationby changing a steered angle of a steered wheel of said vehicle such thata traveling position of said vehicle is kept at a predetermined positionin a lane in a lane width direction based on said lane information and alane changing assist control to assist said driver with said steeringoperation by changing said steered angle such that said vehicle changesa lane from an original lane on which said vehicle is currentlytraveling to a target lane adjacent to said original lane based on saidlane information; non-holding detection means for detecting anon-holding state which is a state where said driver of said vehicle isnot holding a steering wheel; and non-holding determination means formeasuring a non-holding duration time which is a time for which saidnon-holding state is continuing during a performance of either said lanetracing assist control or said lane changing assist control to determinewhether or not a first non-holding condition that said non-holdingduration time is more than or equal to a predetermined first time issatisfied, wherein, said steering assist control means is configured to;during a performance of said lane tracing assist control, stop said lanetracing assist control when said first non-holding condition isdetermined to be satisfied, and during a performance of said lanechanging assist control, continue said lane changing assist controluntil a completion condition of said lane changing assist controlbecomes satisfied regardless of said non-holding duration time; and notperform said lane tracing assist control when said first non-holdingcondition is determined to be satisfied at a point in time when saidcompletion condition of said lane changing assist control has beensatisfied.